On Wed, 1 Oct 2008, lcdpublishing wrote:
> I am about 85~90% reliable with my current process doing traces that
> are .015" (380 microns). I would like to get down to .008"~.010"
> (200 to 254 microns).
With toner transfer, 10/10 is quite easy. I've made my own board for a
0.4mm pitch LQFP-80 package, which will be something like 8/8. The biggest
problem I found was not broken traces, but shorts due to paper fragments
getting stuck between the fine gaps between traces and preventing full
etching. The trouble is you can't scrub the paper remnants off too harshly
because the thin etch resist with 0.2mm traces and 0.2mm spacing is very
easy to break (and it means it takes quite a long time to prepare the
board for etching). I use a clothes iron for the transfer process. 10/10
seems about an order of magnitude easier to do than 8/8.
So I've decided for when I'm doing stuff with a 0.4mm pitch components,
I'll send it off to a board house :-) (Which offers some other advantages
such as smaller vias and gives me more flexibility about where I put vias,
for the tradeoff of extra cost and time waiting for the boards to come
back).